His choice of the word “extorted” is illuminating. Mr. Rosenstein is right to say Justice and FBI aren’t obliged to “just open our doors to allow Congress to come and rummage through the files.”

But that isn’t happening here. In the cases at hand, Congress is acting through its committees as a separate and co-equal branch of government—the branch that funds Justice and has the right and obligation to exercise oversight. Congress is making specific requests regarding specific questions and documents.

As for the articles of impeachment, these too are expressions of Congress’s power. The practical worth of contempt and impeachment actions is less about removing an official from power than leverage to encourage cooperation. We had a demonstration of how this works in January, when Mr. Rosenstein and the new FBI director, Christopher Wray, tried to make an end run around the House Intelligence Committee’s subpoenas for information about the Steele dossier on Donald Trump. Only when Speaker Paul Ryan said Congress would hold them in contempt if they didn’t comply did they turn over the documents.

Mr. Rosenstein’s irritation might be warranted if the documents produced so far demonstrated that Congress’s demands were frivolous or imperiled national security. But remember how Justice warned the Intelligence Committee that making public its report on FISA warrants would be “extraordinarily reckless”? Instead, it provided the public with welcome (but still incomplete) insight about what went down in the 2016 election.

Or take the recently released memos written by then-FBI director James Comey to “memorialize” his private conversations with Donald Trump. We can see why Mr. Comey might not want it known that he assured Mr. Trump he didn’t leak or “do weasel things.” Now that everyone’s seen the memos, it’s clear nothing in them justifies the stonewalling before they were turned over to Congress. . . .

Justice can legitimately withhold information from Congress that might jeopardize specific criminal cases. But that doesn’t seem relevant here. We don’t want to see Mr. Rosenstein fired or impeached, but he and the FBI need to recognize Congress’s constitutional authority.